The present invention relates generally to a cannulated screw system for use in orthopedic surgery. Bone screws are generally installed after a screw hole has been separately drilled. As such, current systems generally require separate hole drilling and screw driving instruments. Furthermore, bone screws used, for example, in maxillofacial applications are typically small and may be difficult to manipulate during installation. Thus, there is a concern in using such small screws in that they may be lost during surgery or may fall into the surgical site. The present invention allows a surgeon to simultaneously drill a screw hole and install a bone screw using a single device. In addition, the present invention allows a surgeon to preload multiple screws onto a screwdriver so that he can quickly manipulate and install multiple screws without removing the screwdriver from the incision area. The preloading of the screws is especially advantageous with the small bone screws used in maxillofacial surgery because it eliminates the need for the surgeon to manipulate multiple small screws on an individual basis, thus reducing the amount of user attention required to interface the screws with the instrument. The screw installation procedure may therefore be performed faster and safer, benefiting both surgeon and patient.
For certain applications, such as when the cannulated screws will be driven into the sternum, a single size or length of screw may not be used universally for all patients because the thickness of the sternum may vary significantly between patients. Thus, the surgeon may select a longer screw for a patient having a thick sternum, and a shorter screw for a patient having a relatively thinner sternum. Regardless of the length or size of the screw, however, it may be desirable that the drilling tip of the installation tool protrude from the end of the screw by the same distance. Thus, there is a need to provide a cannulated screw installation tool that can accept cannulated screws of different sizes and lengths, while maintaining a drilling tip that protrudes from the each screw by the same amount.